1. Field of the Invention
The present invention relates to an organic light emitting device, and more particularly, to a passivation layer of an organic light emitting device.
2. Discussion of the Related Art
Although a liquid crystal display device has been widely used as a flat panel display device, the liquid crystal display device requires a backlight as a separate light source and has technical limitations in view of brightness and contrast ratio. In this respect, attention to an organic light emitting device which is relatively excellent in brightness and contrast ratio has been increased.
The organic light emitting device has a structure in which a light emitting layer is interposed between a cathode and an anode, wherein electrons are generated in the cathode, and holes are generated in the anode. If the electrons generated in the cathode and the holes generated in the anode are injected into the light emitting layer, excitons are generated by combination of the injected electrons and holes, and then the generated excitons are changed from the excited state to a ground state, whereby light is emitted. In this way, the organic light emitting device displays a picture image.
Hereinafter, an organic light emitting device according to the related art will be described with reference to the accompanying drawing.
FIG. 1 is a brief cross-sectional view illustrating an organic light emitting device according to the related art.
As shown in FIG. 1, the organic light emitting device of the related art includes a first substrate 10, a light emitting device layer 20, a passivation layer 30, an adhesive layer 40, and a second substrate 50.
The light emitting device layer 20 is formed on the first substrate 10. The light emitting device layer 20 includes a thin film transistor layer 21 formed on the first substrate 10 and a light emitting diode layer 22 formed on the thin film transistor layer 21.
The passivation layer 30 is formed on the light emitting device layer 20. The passivation layer 30 serves to prevent water from being permeated into the light emitting device layer 20. This passivation layer 30 includes an inorganic insulating film such as SiNx.
The adhesive layer 40 is formed on the passivation layer 30. The adhesive layer 40 serves to adhere the second substrate 50 onto the passivation layer 30.
The second substrate 50 is formed on the adhesive layer 40, and serves to protect the organic light emitting device from external impact.
The aforementioned organic light emitting device of the related art has problems as follows.
The inorganic insulating film such as SiNx used as the passivation layer 30 may be deposited by plasma enhanced chemical vapor deposition (PECVD) or sputtering. If the inorganic insulating film is deposited using the sputtering method, the organic light emitting layer constituting the light emitting diode layer 22 may be damaged. Accordingly, the inorganic insulating film is mainly deposited using the PECVD method.
Also, if the inorganic insulating film is deposited using the PECVD method, the deposition process should be performed at a temperature less than a glass transition temperature Tg of the organic light emitting layer. Accordingly, the deposition process is performed for the inorganic insulating film at a temperature of 100° C. or less. Meanwhile, the inorganic insulating film obtained through such a deposition process contains a lot of hydrogen (H) decomposed from source gases such as SiH4 and NH3.
As described above, according to the light emitting device of the related art, the passivation layer 30 contains a lot of H. If the passivation layer 30 contains a lot of H, H moves downwardly as time passes, and thus H may become diffused into an active layer of the thin film transistor layer 21. In this way, if H is diffused into the active layer, H oxidizes a semiconductor constituting the active layer, and consequently a threshold voltage of the thin film transistor is changed. As a result, a problem occurs in that picture quality which is displayed is deteriorated.